Abstract

This Ph.D. thesis in Physics is focused on the study of the thermal and mechanical performances of the silicon pixel detector used in the NA62 experiment at CERN. This detector, named GigaTracker, is very important, because it is enclosed in a tracking system which has to measure the impulse of incident particles; this system has also to track the trajectories of the particles.
In the first chapter (NA62 physics) the motivations of the experiment are discussed; initially the discussion is focused on the discrete operators C, P, T. Afterwards the CP and CPT symmetries are explained. Finally there is a discussion about the CP violation and its consequences. The CKM matrix is presented as well, with the existing relation between its structure and the CP violation. The NA62 experiment is realized in order to allow the measurement of the branching ratio (BR) of the rare decay K+ → π+ . The purpose is to reveal at least 80 of such events, in order to test the validity of the Standard Model; the verification is performed by means of the measurement of the |Vtd| parameter, which is inserted in the CKM (Cabibbo-Kobayashi-Maskawa) matrix.
In the second chapter (experimental setup and revealers) the technological aspects regarding the experiment are explained in detail. First of all, a discussion about the revealers is given, especially about their mechanical structure. The NA62 experiment takes place at the CERN SPS (Super Proton Synchrotron); the optics of the K12 line is discussed: the line convoys the beam up to the revealers.
In the third chapter (The Gigatracker and the problem about its heat power consumption) the GigaTracker’s mechanical structure is explained in detail; the electrical aspects are discussed as well. The silicon pixel detector utilized in the GigaTracker stations is interested by a very high particle rate. This causes a relevant heat generation and consequently the temperature of the silicon detector increases. There is the necessity of a high performance cooling system, able to keep the temperature at a low level; in this way the life durability of the detector is expected to be about one hundred days.
In the fourth chapter (simulations with the I-DEAS 12 software) the explanation of a proper cooling system for the GigaTracker is given. The project has been carried out using a CAD (Computer Aided Design) named I-DEAS 12. Some different kinds of cooling systems are presented and discussed: in these projects, a pipe convoys a cooling gas (nitrogen). Finally there is a dissertation regarding the GigaTracker prototype realized in the mechanical laboratory of the section of Ferrara of the INFN.